Privacy-preserving anomalous behavior detection

ABSTRACT

An example operation may include one or more of storing a tree structure via a blockchain storage, the tree structure comprising anonymous behavior data of a plurality of blockchain participants stored in a plurality of nodes in a hierarchical structure, receiving a request to add new anonymous behavior data to the tree structure, the request comprising a zero-knowledge proof generated by a blockchain participant, identifying an active leaf on the tree structure which stores previously recorded anonymous behavior data of the blockchain participant associated with the request based on the zero-knowledge proof, generating a new active leaf for the blockchain participant based on the new anonymous behavior data and the previously recorded anonymous behavior, and storing the new active leaf as a leaf node on the tree structure in the blockchain storage.

TECHNICAL FIELD

This application generally relates to a process for tracking behavioranonymously, and more particularly, to a blockchain which manage astorage structure for tracking data without knowing or revealing anidentify of the participant whose data is being tracked.

BACKGROUND

A centralized database stores and maintains data in a single database(e.g., a database server) at one location. This location is often acentral computer, for example, a desktop central processing unit (CPU),a server CPU, or a mainframe computer. Information stored on acentralized database is typically accessible from multiple differentpoints. Multiple users or client workstations can work simultaneously onthe centralized database, for example, based on a client/serverconfiguration. A centralized database is easy to manage, maintain, andcontrol, especially for purposes of security because of its singlelocation. Within a centralized database, data redundancy is minimized asa single storing place of all data also implies that a given set of dataonly has one primary record.

However, a centralized database suffers from significant drawbacks. Forexample, a centralized database has a single point of failure. Inparticular, if there are no fault-tolerance considerations and ahardware failure occurs (for example a hardware, firmware, and/or asoftware failure), all data within the database is lost and work of allusers is interrupted. In addition, centralized databases are highlydependent on network connectivity. As a result, the slower theconnection, the amount of time needed for each database access isincreased. Another drawback is the occurrence of bottlenecks when acentralized database experiences high traffic due to a single location.Furthermore, a centralized database provides limited access to databecause only one copy of the data is maintained by the database. As aresult, multiple devices cannot access the same piece of data at thesame time without creating significant problems or risk overwritingstored data. Furthermore, because a database storage system has minimalto no data redundancy, data that is unexpectedly lost is very difficultto retrieve other than through manual operation from back-up storage.

In effort to address the deficiencies in security, immutability, andcentral authority, organizations have begun turning to blockchain tostore data. For example, supply chain data (e.g., between differentuntrusting participants of the supply chain, etc.) may be recorded in atrusted manner through the use of blockchain. However, typically theinformation stored on the blockchain is viewable/available to all of theparticipants of the blockchain. As such, what is needed is a solutionthat can track information anonymously.

SUMMARY

One example embodiment provides a system that includes one or more of astorage configured to a tree structure, the tree structure comprisinganonymous behavior data of a plurality of blockchain participants storedin a plurality of nodes in a hierarchical structure, and a processorconfigured to one or more of receive a request to add new anonymousbehavior data to the tree structure which comprises a zero-knowledgeproof generated by a blockchain participant, identify an active leaf onthe tree structure which stores previously recorded anonymous behaviordata of the blockchain participant associated with the request based onthe zero-knowledge proof, and generate a new active leaf for theblockchain participant based on the new anonymous behavior data and thepreviously recorded anonymous behavior, wherein the storage is furtherconfigured to store the new active leaf as a leaf node on the treestructure.

Another example embodiment provides a method that includes one or moreof storing a tree structure via a blockchain storage, the tree structurecomprising anonymous behavior data of a plurality of blockchainparticipants stored in a plurality of nodes in a hierarchical structure,receiving a request to add new anonymous behavior data to the treestructure, the request comprising a zero-knowledge proof generated by ablockchain participant, identifying an active leaf on the tree structurewhich stores previously recorded anonymous behavior data of theblockchain participant associated with the request based on thezero-knowledge proof, generating a new active leaf for the blockchainparticipant based on the new anonymous behavior data and the previouslyrecorded anonymous behavior, and storing the new active leaf as a leafnode on the tree structure in the blockchain storage.

A further example embodiment provides a non-transitory computer readablemedium comprising instructions, that when read by a processor, cause theprocessor to perform one or more of storing a tree structure via ablockchain storage, the tree structure comprising anonymous behaviordata of a plurality of blockchain participants stored in a plurality ofnodes in a hierarchical structure, receiving a request to add newanonymous behavior data to the tree structure, the request comprising azero-knowledge proof generated by a blockchain participant, identifyingan active leaf on the tree structure which stores previously recordedanonymous behavior data of the blockchain participant associated withthe request based on the zero-knowledge proof, generating a new activeleaf for the blockchain participant based on the new anonymous behaviordata and the previously recorded anonymous behavior, and storing the newactive leaf as a leaf node on the tree structure in the blockchainstorage.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a blockchain network including storingbehavior data of supply chain participants, according to exampleembodiments.

FIG. 2A is a diagram illustrating an example blockchain architectureconfiguration, according to example embodiments.

FIG. 2B is a diagram illustrating a blockchain transactional flow,according to example embodiments.

FIG. 3A is a diagram illustrating a permissioned network, according toexample embodiments.

FIG. 3B is a diagram illustrating another permissioned network,according to example embodiments.

FIG. 4A is a diagram illustrating a process of adding a new active leafnode to a blockchain structure, according to example embodiments.

FIG. 4B is a diagram illustrating a process of invoking a new activeleaf node by a blockchain participant, according to example embodiments.

FIG. 4C is a diagram illustrating a queue which is implemented via ablockchain ledger for preventing storage conflicts, according to exampleembodiments.

FIG. 5A is a flow diagram illustrating a method of updating anonymousbehavior on a blockchain structure, according to example embodiments.

FIG. 5B is a flow diagram illustrating a method of managing a queue viaa blockchain ledger, according to example embodiments.

FIG. 6A is a diagram illustrating an example system configured toperform one or more operations described herein, according to exampleembodiments.

FIG. 6B is a diagram illustrating another example system configured toperform one or more operations described herein, according to exampleembodiments.

FIG. 6C is a diagram illustrating a further example system configured toutilize a smart contract, according to example embodiments.

FIG. 6D is a diagram illustrating yet another example system configuredto utilize a blockchain, according to example embodiments.

FIG. 7A is a diagram illustrating a process for a new block being addedto a distributed ledger, according to example embodiments.

FIG. 7B is a diagram illustrating contents of a new data block,according to example embodiments.

FIG. 7C is a diagram illustrating a blockchain for digital content,according to example embodiments.

FIG. 7D is a diagram illustrating a block which may represent thestructure of blocks in the blockchain, according to example embodiments.

FIG. 8 is a diagram illustrating an example system that supports one ormore of the example embodiments.

DETAILED DESCRIPTION

It will be readily understood that the instant components, as generallydescribed and illustrated in the figures herein, may be arranged anddesigned in a wide variety of different configurations. Thus, thefollowing detailed description of the embodiments of at least one of amethod, apparatus, non-transitory computer readable medium and system,as represented in the attached figures, is not intended to limit thescope of the application as claimed but is merely representative ofselected embodiments.

The instant features, structures, or characteristics as describedthroughout this specification may be combined or removed in any suitablemanner in one or more embodiments. For example, the usage of the phrases“example embodiments”, “some embodiments”, or other similar language,throughout this specification refers to the fact that a particularfeature, structure, or characteristic described in connection with theembodiment may be included in at least one embodiment. Thus, appearancesof the phrases “example embodiments”, “in some embodiments”, “in otherembodiments”, or other similar language, throughout this specificationdo not necessarily all refer to the same group of embodiments, and thedescribed features, structures, or characteristics may be combined orremoved in any suitable manner in one or more embodiments.

In addition, while the term “message” may have been used in thedescription of embodiments, the application may be applied to many typesof networks and data. Furthermore, while certain types of connections,messages, and signaling may be depicted in exemplary embodiments, theapplication is not limited to a certain type of connection, message, andsignaling.

Example embodiments provide methods, systems, components, non-transitorycomputer readable media, devices, and/or networks, which provide asystem and method for privacy-preserving anomalous behavior detectionand tracking.

In one embodiment the system utilizes a decentralized database (such asa blockchain) that is a distributed storage system, which includesmultiple nodes that communicate with each other. The decentralizeddatabase includes an append-only immutable data structure resembling adistributed ledger capable of maintaining records between mutuallyuntrusted parties. The untrusted parties are referred to herein as peersor peer nodes. Each peer maintains a copy of the database records and nosingle peer can modify the database records without a consensus beingreached among the distributed peers. For example, the peers may executea consensus protocol to validate blockchain storage transactions, groupthe storage transactions into blocks, and build a hash chain over theblocks. This process forms the ledger by ordering the storagetransactions, as is necessary, for consistency. In various embodiments,a permissioned and/or a permissionless blockchain can be used. In apublic or permission-less blockchain, anyone can participate without aspecific identity. Public blockchains often involve nativecryptocurrency and use consensus based on various protocols such asProof of Work (PoW). On the other hand, a permissioned blockchaindatabase provides secure interactions among a group of entities whichshare a common goal but which do not fully trust one another, such asbusinesses that exchange funds, goods, information, and the like.

This system can utilize a blockchain that operates arbitrary,programmable logic, tailored to a decentralized storage scheme andreferred to as “smart contracts” or “chaincodes.” In some cases,specialized chaincodes may exist for management functions and parameterswhich are referred to as system chaincode. The application can furtherutilize smart contracts that are trusted distributed applications whichleverage tamper-proof properties of the blockchain database and anunderlying agreement between nodes, which is referred to as anendorsement or endorsement policy. Blockchain transactions associatedwith this application can be “endorsed” before being committed to theblockchain while transactions, which are not endorsed, are disregarded.An endorsement policy allows chaincode to specify endorsers for atransaction in the form of a set of peer nodes that are necessary forendorsement. When a client sends the transaction to the peers specifiedin the endorsement policy, the transaction is executed to validate thetransaction. After validation, the transactions enter an ordering phasein which a consensus protocol is used to produce an ordered sequence ofendorsed transactions grouped into blocks.

This system can utilize nodes that are the communication entities of theblockchain system. A “node” may perform a logical function in the sensethat multiple nodes of different types can run on the same physicalserver. Nodes are grouped in trust domains and are associated withlogical entities that control them in various ways. Nodes may includedifferent types, such as a client or submitting-client node whichsubmits a transaction-invocation to an endorser (e.g., peer), andbroadcasts transaction-proposals to an ordering service (e.g., orderingnode). Another type of node is a peer node which can receive clientsubmitted transactions, commit the transactions and maintain a state anda copy of the ledger of blockchain transactions. Peers can also have therole of an endorser, although it is not a requirement. Anordering-service-node or orderer is a node running the communicationservice for all nodes, and which implements a delivery guarantee, suchas a broadcast to each of the peer nodes in the system when committingtransactions and modifying a world state of the blockchain, which isanother name for the initial blockchain transaction which normallyincludes control and setup information.

This system can utilize a ledger that is a sequenced, tamper-resistantrecord of all state transitions of a blockchain. State transitions mayresult from chaincode invocations (i.e., transactions) submitted byparticipating parties (e.g., client nodes, ordering nodes, endorsernodes, peer nodes, etc.). Each participating party (such as a peer node)can maintain a copy of the ledger. A transaction may result in a set ofasset key-value pairs being committed to the ledger as one or moreoperands, such as creates, updates, deletes, and the like. The ledgerincludes a blockchain (also referred to as a chain) which is used tostore an immutable, sequenced record in blocks. The ledger also includesa state database which maintains a current state of the blockchain.

This system can utilize a chain that is a transaction log which isstructured as hash-linked blocks, and each block contains a sequence ofN transactions where N is equal to or greater than one. The block headerincludes a hash of the block's transactions, as well as a hash of theprior block's header. In this way, all transactions on the ledger may besequenced and cryptographically linked together. Accordingly, it is notpossible to tamper with the ledger data without breaking the hash links.A hash of a most recently added blockchain block represents everytransaction on the chain that has come before it, making it possible toensure that all peer nodes are in a consistent and trusted state. Thechain may be stored on a peer node file system (i.e., local, attachedstorage, cloud, etc.), efficiently supporting the append-only nature ofthe blockchain workload.

The current state of the immutable ledger represents the latest valuesfor all keys that are included in the chain transaction log. Since thecurrent state represents the latest key values known to a channel, it issometimes referred to as a world state. Chaincode invocations executetransactions against the current state data of the ledger. To make thesechaincode interactions efficient, the latest values of the keys may bestored in a state database. The state database may be simply an indexedview into the chain's transaction log, it can therefore be regeneratedfrom the chain at any time. The state database may automatically berecovered (or generated if needed) upon peer node startup, and beforetransactions are accepted.

The example embodiments provide a system that has the ability toanonymously track the behavior (and detect anomalous behavior) of anentity (e.g. a supply-chain participant, a patient, a gaming user, etc.)on blockchain, based on storing and updating some relevant statisticsrelated to the entity's inputs (e.g. ratings to a supplier, medicalrecords, gaming information, etc.) while preserving the privacy of theentity. According to various aspects, the system can maintain a Merkletree for some entities (e.g., a supplier) that participate in theblockchain. Each Merkle tree may include an “active leaf” for each user(e.g., a buyer) of that entity (e.g., supplier).

The buyer's “active leaf” may store a standard cryptographic hash (e.g.,sha256) value of a pre-image that includes a concatenation of a secret(known only to the Buyer) which is a random bit string, its currentrating sum (encoded as a bit string), and its current number of ratings(encoded as a bit string). Therefore, an accumulation of the buyer'sanonymous activity/behavior can be stored in the active leaf node basedon a total number of reviews plus the summation of all the ratingsprovided by the buyer. Accordingly, a rating history of a buyer may bemaintained anonymously, without the need to disclose an identity of thebuyer.

Some benefits of the instant solutions described and depicted hereininclude the ability to accumulate behavioral information about aparticipant of the blockchain while still preserving the privacy of theparticipant. Although the examples described herein refer to theanonymous behavior of a buyer providing reviews/ratings to a seller in asupply chain network, the example embodiments are not limited thereto.As another example, anonymous bidding on blockchain may be tracked. Inthis example, the bidders are anonymous and are allowed to update theirbids up to a fixed number of times. The auctioneer can detect a bidder'sanomalous bid sequence using the example embodiments wherein the activeleaf of a bidder stores the cryptographic hash of the number of bidupdates made and the zero-knowledge proof verifies that this number isbelow a threshold.

As another example, the embodiments may be used for anonymous patienthealth monitoring. In this example, the blockchain may maintain a systemto detect anomalies in the sequence of health indicator datapoints ofpatients. For each patient, measurements of some indicator of thepatient's health may be taken periodically and sent as anonymous inputsto the system. In this example, a datapoint which is outside apredefined region (e.g., such as described by the mean and/or varianceof the sequence, etc.) may be considered anomalous. This can be detectedusing the system described in the example embodiments wherein the activeleaf of a patient stores the cryptographic hash of the number ofdatapoints, the current sum, and current sum of squares, which aresufficient to compute and update the mean and variance. Thezero-knowledge proof can be used to ensure that the new datapoint iswithin the region described by the current mean and variance.

FIG. 1 illustrates a blockchain network 100 including storing behaviordata of supply chain participants, according to example embodiments.Referring to FIG. 1, the blockchain network 100 includes a blockchain120 which stores supply chain data between suppliers 111 and 112 andbuyers 131, 132, 133, and 134. For example, the blockchain 120 may storework orders, invoices, signed documents, digital goods, and the like.Although not shown in FIG. 1, the blockchain 120 may be implemented by aplurality of peer nodes which may include committing nodes, endorsernodes, orderer nodes, and the like. In some cases, a node may fulfillmore than one node role.

According to various embodiments, the nodes that implement theblockchain 120 may each maintain smart contracts (which are executablechaincode), a ledger distributed/replicated among the nodes, and animmutable chain of blocks which are stored on the ledger. The ledger maybe a key-value store (KVS) accessible to the smart contracts which areexecuted to programmatically maintain and update data on the ledger. Thesuppliers 111 and 112 and the buyers 131-134 may access the blockchain120 via one or more trusted nodes.

According to various embodiments, behavior data of the participants ofthe supply chain may be stored anonymously via the blockchain 120. Forexample, the smart contracts implemented by the nodes of the blockchain120 may store and manage Merkle trees (or other data structures) askey-values in the ledger which can be used to anonymously store behaviorinformation of the buyers 131-134, in this example. The execution of asmart contracts are transactions consisting of read and write sets ofthe key-values accessed during the execution. These sets are included ina block of transactions appended to the chain of blocks on theblockchain 120. The ledger and the chain of blocks are identicallyupdated on every peer in the blockchain network according to a consensusprotocol.

In the examples herein, behavior such as ratings and reviews of theSuppliers 111-112 performed by the buyers 131-134 may be recorded on theMerkle trees in the key-value store of the blockchain 120. In someembodiments, the nodes may maintain a separate Merkle tree for eachsupplier 111 and 112 and each buyer 131, 132, 133, and 134 may have adedicated active leaf in the respective Merkle trees. To implement theanonymous accumulation of data such as ratings/reviews over time, thenodes may rely on non-interactive zero knowledge proofs with (i) thebuyer (client) generating the proof, and (ii) the smart contract(chaincode) verifying the proof against the ledger's data. Thezero-knowledge proof allows a buyer to submit new review information andnullify old review information while preserving an identity of thebuyer. In other words, new active leaves are added (and used)anonymously. The smart contracts may include API enhancements toefficiently achieve shared anonymous data update.

As the buyers 131-134 and suppliers 111-112 engage in supply chainactivities, the buyers may continuously upload reviews regarding thesuppliers 111-112 in an anonymous way ensuring that both the suppliers111-112 are performing well, and also to ensure that buyers 131-134 arenot continuously giving negative reviews.

FIG. 2A illustrates a blockchain architecture configuration 200,according to example embodiments. Referring to FIG. 2A, the blockchainarchitecture 200 may include certain blockchain elements, for example, agroup of blockchain nodes 202. The blockchain nodes 202 may include oneor more nodes 204-210 (these four nodes are depicted by example only).These nodes participate in a number of activities, such as blockchaintransaction addition and validation process (consensus). One or more ofthe blockchain nodes 204-210 may endorse transactions based onendorsement policy and may provide an ordering service for allblockchain nodes in the architecture 200. A blockchain node may initiatea blockchain authentication and seek to write to a blockchain immutableledger stored in blockchain layer 216, a copy of which may also bestored on the underpinning physical infrastructure 214. The blockchainconfiguration may include one or more applications 224 which are linkedto application programming interfaces (APIs) 222 to access and executestored program/application code 220 (e.g., chaincode, smart contracts,etc.) which can be created according to a customized configurationsought by participants and can maintain their own state, control theirown assets, and receive external information. This can be deployed as atransaction and installed, via appending to the distributed ledger, onall blockchain nodes 204-210.

The blockchain base or platform 212 may include various layers ofblockchain data, services (e.g., cryptographic trust services, virtualexecution environment, etc.), and underpinning physical computerinfrastructure that may be used to receive and store new transactionsand provide access to auditors which are seeking to access data entries.The blockchain layer 216 may expose an interface that provides access tothe virtual execution environment necessary to process the program codeand engage the physical infrastructure 214. Cryptographic trust services218 may be used to verify transactions such as asset exchangetransactions and keep information private.

The blockchain architecture configuration of FIG. 2A may process andexecute program/application code 220 via one or more interfaces exposed,and services provided, by blockchain platform 212. The code 220 maycontrol blockchain assets. For example, the code 220 can store andtransfer data, and may be executed by nodes 204-210 in the form of asmart contract and associated chaincode with conditions or other codeelements subject to its execution. As a non-limiting example, smartcontracts may be created to execute reminders, updates, and/or othernotifications subject to the changes, updates, etc. The smart contractscan themselves be used to identify rules associated with authorizationand access requirements and usage of the ledger. For example, anonymousdata 226 may be processed by one or more processing entities (e.g.,virtual machines) included in the blockchain layer 216. The result 228may include new active leaf data for a Merkle tree stored on theblockchain in association with the anonymous data 226. The physicalinfrastructure 214 may be utilized to retrieve any of the data orinformation described herein.

A smart contract may be created via a high-level application andprogramming language, and then written to a block in the blockchain. Thesmart contract may include executable code which is registered, stored,and/or replicated with a blockchain (e.g., distributed network ofblockchain peers). A transaction is an execution of the smart contractcode which can be performed in response to conditions associated withthe smart contract being satisfied. The executing of the smart contractmay trigger a trusted modification(s) to a state of a digital blockchainledger. The modification(s) to the blockchain ledger caused by the smartcontract execution may be automatically replicated throughout thedistributed network of blockchain peers through one or more consensusprotocols.

The smart contract may write data to the blockchain in the format ofkey-value pairs. Furthermore, the smart contract code can read thevalues stored in a blockchain and use them in application operations.The smart contract code can write the output of various logic operationsinto the blockchain. The code may be used to create a temporary datastructure in a virtual machine or other computing platform. Data writtento the blockchain can be public and/or can be encrypted and maintainedas private. The temporary data that is used/generated by the smartcontract is held in memory by the supplied execution environment, thendeleted once the data needed for the blockchain is identified.

A chaincode may include the code interpretation of a smart contract,with additional features. As described herein, the chaincode may beprogram code deployed on a computing network, where it is executed andvalidated by chain validators together during a consensus process. Thechaincode receives a hash and retrieves from the blockchain a hashassociated with the data template created by use of a previously storedfeature extractor. If the hashes of the hash identifier and the hashcreated from the stored identifier template data match, then thechaincode sends an authorization key to the requested service. Thechaincode may write to the blockchain data associated with thecryptographic details.

FIG. 2B illustrates an example of a blockchain transactional flow 250between nodes of the blockchain in accordance with an exampleembodiment. Referring to FIG. 2B, the transaction flow may include atransaction proposal 291 sent by an application client node 260 to anendorsing peer node 281. The endorsing peer 281 may verify the clientsignature and execute a chaincode function to initiate the transaction.The output may include the chaincode results, a set of key/valueversions that were read in the chaincode (read set), and the set ofkeys/values that were written in chaincode (write set). The proposalresponse 292 is sent back to the client 260 along with an endorsementsignature, if approved. The client 260 assembles the endorsements into atransaction payload 293 and broadcasts it to an ordering service node284. The ordering service node 284 then delivers ordered transactions asblocks to all peers 281-283 on a channel. Before committal to theblockchain, each peer 281-283 may validate the transaction. For example,the peers may check the endorsement policy to ensure that the correctallotment of the specified peers have signed the results andauthenticated the signatures against the transaction payload 293.

Referring again to FIG. 2B, the client node 260 initiates thetransaction 291 by constructing and sending a request to the peer node281, which is an endorser. The client 260 may include an applicationleveraging a supported software development kit (SDK), which utilizes anavailable API to generate a transaction proposal. The proposal is arequest to invoke a chaincode function so that data can be read and/orwritten to the ledger (i.e., write new key value pairs for the assets).The SDK may serve as a shim to package the transaction proposal into aproperly architected format (e.g., protocol buffer over a remoteprocedure call (RPC)) and take the client's cryptographic credentials toproduce a unique signature for the transaction proposal.

In response, the endorsing peer node 281 may verify (a) that thetransaction proposal is well formed, (b) the transaction has not beensubmitted already in the past (replay-attack protection), (c) thesignature is valid, and (d) that the submitter (client 260, in theexample) is properly authorized to perform the proposed operation onthat channel. The endorsing peer node 281 may take the transactionproposal inputs as arguments to the invoked chaincode function. Thechaincode is then executed against a current state database to producetransaction results including a response value, read set, and write set.However, no updates are made to the ledger at this point. In 292, theset of values, along with the endorsing peer node's 281 signature ispassed back as a proposal response 292 to the SDK of the client 260which parses the payload for the application to consume.

In response, the application of the client 260 inspects/verifies theendorsing peers signatures and compares the proposal responses todetermine if the proposal response is the same. If the chaincode onlyqueried the ledger, the application would inspect the query response andwould typically not submit the transaction to the ordering node service284. If the client application intends to submit the transaction to theordering node service 284 to update the ledger, the applicationdetermines if the specified endorsement policy has been fulfilled beforesubmitting (i.e., did all peer nodes necessary for the transactionendorse the transaction). Here, the client may include only one ofmultiple parties to the transaction. In this case, each client may havetheir own endorsing node, and each endorsing node will need to endorsethe transaction. The architecture is such that even if an applicationselects not to inspect responses or otherwise forwards an unendorsedtransaction, the endorsement policy will still be enforced by peers andupheld at the commit validation phase.

After successful inspection, in step 293 the client 260 assemblesendorsements into a transaction and broadcasts the transaction proposaland response within a transaction message to the ordering node 284. Thetransaction may contain the read/write sets, the endorsing peerssignatures and a channel ID. The ordering node 284 does not need toinspect the entire content of a transaction in order to perform itsoperation, instead the ordering node 284 may simply receive transactionsfrom all channels in the network, order them chronologically by channel,and create blocks of transactions per channel.

The blocks of the transaction are delivered from the ordering node 284to all peer nodes 281-283 on the channel. The transactions 294 withinthe block are validated to ensure any endorsement policy is fulfilledand to ensure that there have been no changes to ledger state for readset variables since the read set was generated by the transactionexecution. Transactions in the block are tagged as being valid orinvalid. Furthermore, in step 295 each peer node 281-283 appends theblock to the channel's chain, and for each valid transaction the writesets are committed to current state database. An event is emitted, tonotify the client application that the transaction (invocation) has beenimmutably appended to the chain, as well as to notify whether thetransaction was validated or invalidated.

FIG. 3A illustrates an example of a permissioned blockchain network 300,which features a distributed, decentralized peer-to-peer architecture.In this example, a blockchain user 302 may initiate a transaction to thepermissioned blockchain 304. In this example, the transaction can be adeploy, invoke, or query, and may be issued through a client-sideapplication leveraging an SDK, directly through an API, etc. Networksmay provide access to a regulator 306, such as an auditor. A blockchainnetwork operator 308 manages member permissions, such as enrolling theregulator 306 as an “auditor” and the blockchain user 302 as a “client”.An auditor could be restricted only to querying the ledger whereas aclient could be authorized to deploy, invoke, and query certain types ofchaincode.

A blockchain developer 310 can write chaincode and client-sideapplications. The blockchain developer 310 can deploy chaincode directlyto the network through an interface. To include credentials from atraditional data source 312 in chaincode, the developer 310 could use anout-of-band connection to access the data. In this example, theblockchain user 302 connects to the permissioned blockchain 304 througha peer node 314. Before proceeding with any transactions, the peer node314 retrieves the user's enrollment and transaction certificates from acertificate authority 316, which manages user roles and permissions. Insome cases, blockchain users must possess these digital certificates inorder to transact on the permissioned blockchain 304. Meanwhile, a userattempting to utilize chaincode may be required to verify theircredentials on the traditional data source 312. To confirm the user'sauthorization, chaincode can use an out-of-band connection to this datathrough a traditional processing platform 318.

FIG. 3B illustrates another example of a permissioned blockchain network320, which features a distributed, decentralized peer-to-peerarchitecture. In this example, a blockchain user 322 may submit atransaction to the permissioned blockchain 324. In this example, thetransaction can be a deploy, invoke, or query, and may be issued througha client-side application leveraging an SDK, directly through an API,etc. Networks may provide access to a regulator 326, such as an auditor.A blockchain network operator 328 manages member permissions, such asenrolling the regulator 326 as an “auditor” and the blockchain user 322as a “client”. An auditor could be restricted only to querying theledger whereas a client could be authorized to deploy, invoke, and querycertain types of chaincode.

A blockchain developer 330 writes chaincode and client-sideapplications. The blockchain developer 330 can deploy chaincode directlyto the network through an interface. To include credentials from atraditional data source 332 in chaincode, the developer 330 could use anout-of-band connection to access the data. In this example, theblockchain user 322 connects to the network through a peer node 334.Before proceeding with any transactions, the peer node 334 retrieves theuser's enrollment and transaction certificates from the certificateauthority 336. In some cases, blockchain users must possess thesedigital certificates in order to transact on the permissioned blockchain324. Meanwhile, a user attempting to utilize chaincode may be requiredto verify their credentials on the traditional data source 332. Toconfirm the user's authorization, chaincode can use an out-of-bandconnection to this data through a traditional processing platform 338.

FIG. 4A illustrates a process 400 of adding a new active leaf node to ablockchain structure 410 (shown in FIG. 4A) which is stored onblockchain 401 (shown in FIG. 4B), according to example embodiments, andFIG. 4B illustrates a process 430 of invoking a new active leaf node411B by a blockchain participant 431, according to example embodiments.In the example of FIG. 4A, the blockchain structure is a Merkle tree 410which includes a first state 410A (also referred to as a current state),and a second state 410B (also referred to as an updated state) in whicha new active leaf node 411B is added and the current active leaf node411A is nullified, anonymously. In the example of FIG. 4A, three activeleaf nodes 411, 412, and 413 are shown and correspond to three anonymousbuyers of a supplier.

As described herein, a Merkle tree is a binary tree that may include adepth d where the tree is a complete binary tree of depth d. In thiscase, each of the leaf nodes store data which may be represented as abit string of a fixed length. The value at each internal node in thetree may be a cryptographic hash (e.g., sha256, etc.) of a concatenationof values of a left and a right child node, in that order. In theexamples herein, an empty Merkle tree may be initialized with all itsleaf nodes set to some default value, for e.g. the all zeros bit string.Any new active leaf is added in place of the next available unused(i.e., having the default value) leaf node in the left to right order,and the values of the nodes on the path from the added leaf node up toand including the root node are updated. For example, for each buyer inthe example of FIG. 1, a first active leaf is added and set to thestandard cryptographic hash of an initial pre-image with a secret (madeknown only to the respective buyer) random bit string, a rating sum ofzero (encoded as a bit string) and the number of ratings as zero(encoded as a bit string). The Merkle tree may be stored on a blockchainas part of the ledger corresponding to the smart contract. In an emptyMerkle tree, all the nodes at the same depth have the same value. Thus,for memory efficiency, only the values of those nodes are explicitlystored which differ from the corresponding node in the empty Merkletree.

As described in the examples herein, each active leaf may store orotherwise include anonymous behavior data of a participant (such as abuyer in the example of FIG. 1). In the examples herein, a smartcontract maintains a Merkle tree for each supplier which contains an“active leaf” for each buyer of that supplier. The attributes that aremaintained within a buyer's “active leaf” may include a standardcryptographic hash (sha256) value of the following pre-image: theconcatenation of (i) a secret (known only to the buyer) random bitstring, (ii) its current rating sum (encoded as a bit string), and (iii)its current number of ratings (encoded as a bit string). In the exampleof FIG. 4B, the current active leaf node 411A includes these respectiveattributes.

When a buyer wants to add a new rating of a supplier, the buyer mayinvoke a smart contract of the blockchain 401. In the example of FIG.4B, an anonymous system 431 (such as one of the buyers 131-134 shown inFIG. 1) may request to update the buyer's active leaf with the supplier.In the example of FIG. 4B, the anonymous system 431 is associated withleaf node 411A and uploads a request 432 which includes a new activeleaf node 411B. When the buyer (anonymous system 431) calls the smartcontract to provide a new rating (request 432), the buyer provides thenew active leaf 411B containing the standard cryptographic hash value ofthe following new pre-image: the concatenation of (i) a new secretrandom bit string (known only to the buyer, (ii) the updated rating sum,and (iii) the updated number of ratings. In addition, the buyer providesa nullifier of the existing active leaf 411A, which is a different,un-linkable cryptographic hash (e.g. sha256 with a non-standardinitialization vector) of the pre-image of the existing active leaf411A. Further, the Buyer provides a zero-knowledge proof (ZKP), as wellas the rating it desires to submit.

According to various embodiments, the ZKP may show that the nullifierprovided is indeed that of an existing active leaf in the Merkle tree,the current average rating given by the ratio of the current rating sumand the current number of ratings, is at least a given threshold (thischeck detects the anomalous behavior), and the new active leaf value isthe standard cryptographic hash of the new pre-image given in 411B suchthat the updated rating sum is the rating sum of the existing activeleaf in (ii) plus the provided rating, and updated number of ratings isthe number of ratings of the existing active leaf in (iii) plus one.

The smart contract may verify that the newly provided nullifier isunused so as to ensure that the buyer must only nullify the currentactive leaf 411A and further verify the zero-knowledge proof providedabove. If the check and verification pass, the list of ratings isupdated with the provided rating, the new active leaf 411B is added tothe Merkle-Tree and the provided nullifier is stored and marked as used.Note that in the above process, which current active leaf is nullifiedis not revealed as the verification is in zero-knowledge. The onlyguarantee is that some active leaf in the Merkle-Tree is nullified.Since multiple buyers exist for a supplier, each having an active leaf,the identity of the specific Buyer who is providing the rating is notrevealed.

In the second state 410B, the existing active leaf 411A is nullified andstays in its location, and the new active leaf 411B associated with thesame anonymous user is added in place of a first default/empty leaf inthe left to right order. In this case, the default leaf signifies thatthis leaf node has some default value currently and has not been used tostore any information yet. Therefore, in the second state 410B, the leafL1 411A stays in place and is marked nullified. The new active leaf L1411B is added in place of the default value.

The algorithm used for the zero-knowledge proof creation may be theZKSnarks which is an open source implementation. Using the includedgadgets, the predicate for the zero-knowledge proof may be implementedin libsnark to generate the proving and verification executables and therespective proving and verification keys. The buyer has the provingexecutable and key. As described above, the buyer computes the newactive leaf and the nullifier of the current active leaf. To generatethe proof, the buyer calls the smart contract to query the the values ofthe sibling nodes on the path from the current active leaf to the root.

The buyer may then privately generate (outside the blockchain/smartcontract) the desired zero-knowledge proof using the libsnark provingexecutable and key with the following input values: the authenticationpath consisting of values on sibling nodes on the path from the currentactive leaf to the root, the components of the current active leaf'spre-image (e.g., the secret random bit string, the current rating sum,and the current number of ratings), the to-be provided new rating, andthe new secret random string of the pre-image of the new active leaf.The output is the zero-knowledge proof which can be verified by a smartcontract on the blockchain 401.

Likewise, when its time to verify the ZKP, the Smart Contract receivesfrom the Buyer the new rating, the nullifier of the current active leaf,the new active leaf and the zero-knowledge proof. The smart contract mayread the value of the Merkle tree root and run the libsnark verificationexecutable along with the verification key with the following inputvalues: the new rating, the nullifier of the current active leaf and thenew active leaf, the Merkle tree root value, and the zero-knowledgeproof.

The output of the above executable is a true/false value indicatingwhether the zero-knowledge proof is verified to prove that the nullifierprovided is indeed that of an existing active leaf in the Merkle tree,the current average rating given by the ratio of the current rating sumand the current number of ratings, is at least a given threshold (thischeck detects the anomalous behavior), and the new active leaf value isthe standard cryptographic hash of the new pre-image. The smart contractmay be executed by an endorsing peer of the blockchain 401 which has thelibsnark verification executable along with the verification key thatwhich are accessible to the smart contract. In these examples, the smartcontract does not know the current active leaf which is being nullified.Since the nullifier is un-linkable to the active leaf and theverification is in zero-knowledge, the smart contract does not gain anyinformation about the current active leaf being nullified and thus theprivacy of the buyer is preserved.

For example, the Smart Contract may be executed on the endorsing peer toverify the zero-knowledge proof provided by a buyer who calls the smartcontract to anonymously add a rating for a supplier. The endorsing peerhas the libsnark verification executable along with the verification keythat are accessible to the smart contract. The zero-knowledge proofverification is done by the smart contract on behalf of the supplier whois guaranteed that anomalous (behavior) ratings by a buyer will bedetected, at the same time preserving the privacy of the buyer.

If successful, the intended operations including the Merkle-Tree update,storing the rating and the nullifier, and the like, are performed by thesmart contract, which involves updating a number of key-values in theledger of the blockchain 401. The corresponding endorsed transactionwhich includes the read and write sets is created by the peer andtransmitted as per the Blockchain protocol to be recorded in a block onthe blockchain 401. The key-values in all the blockchain peers' ledgersare identically updated.

FIG. 4C illustrates a process 440 of managing a queue 450 which isimplemented via a blockchain ledger and which can be used to preventstorage conflicts, according to example embodiments. In the Merkle treedescribed herein (or other shared or joint storage structure), a singleinvoke transaction uses a current active leaf and adds a new active leaffor a buyer. This can be done anonymously using the zero-knowledgeproof. However, a problem may occur when multiple buyers (or otherusers) invoke the use/add-leaf transaction at the same time when addinga new leaf at the same index. This simultaneously invocation can lead toread/write conflicts (ref. Hyperledger Fabric v1), thus in each block atmost one add leaf is possible. When the add-leaf operation isnon-anonymous, conflicts can be resolved by collecting the new leavesand adding them in one aggregate transaction. However, this is notpossible in an anonymous data storage because privacy is preserved.Although described with respect to a Merkle tree, a storage conflict cannaturally arise in other zero-knowledge proof paradigms when using anykind of shared data structure modifiable anonymously by multipleparties.

To address this situation, a blockchain peer node 460 (smart contracts)may implement a queue 450 within a distributed blockchain ledger wherenew active leaf nodes (e.g., nodes 411B, 413B, 417C, and 415B) can betemporarily stored and subsequently added to the Merkle tree 410 inresponse to a flush operation. Once the ZK proof is verified, thenullifier is stored, and the rating is added, no additional informationis needed for adding the new active leaf other than its value. The peernode 460 may store a collection of new active leaves in the queue 450which can then be individually added together in a single transaction.

A smart contract application programming interface (API) framework maysupport special a BufferKeys operation which simulates afirst-in-first-out (FIFO) queue 450 of string values. The queue 450 (orbuffer) may be manipulated using various operations, including aDefineBufferKey operation which defines a particular key string to be abuffer key with an optional maximum size of buffer (e.g.,DefineBufferKey(“Supplier1˜MT1˜LeafBuf”, 50)). The API framework mayalso support a BufPush operation which appends a value to an end of thequeue 450. At the endorsement phase, the corresponding (BufferKey,value) write-set pair is generated. During block commitment on ledger,the values for a BufferKey are appended in the order of the transactionsin the block. E.g. BufPush(“Supplier1˜MT1˜LeafBuf”, “1234”). The APIframework may also support a BufFlush operation which returns aniterator to the values in the BufferKey, and the queue is flushed atcommit phase. A transaction cannot have both a BufPush and BufFlush forthe same key. Endorsement includes the BufferKey in a special flush set(e.g., BufFlush(“Supplier1˜MT1˜LeafBuf”)).

Accordingly, the queue 450 and the supporting push and flush operationscan prevent a potential problem of conflict when multiple buyers attemptthe add leaf operation on the Merkle tree simultaneously. This arisesdue to a common data structure, such as the Merkle tree, beingmodifiable anonymously by multiple parties (e.g., buyers). Theoperations such as BufferKeys along with the DefineBufferKey, BufPushand BufFlush operations in the Smart Contract API can be used tosimulate a FIFO queue natively implemented in the blockchain ledger.

Using this enhancement, in the add-leaf operation the smart contract maypush the new active leaf on a predefined BufferKey using the BufPushoperation. Periodically, a designated party calls the BufFlush operation(e.g., chaincode of a designated peer, etc.) iterating through the to-beadded active leaves and adds them to the Merkle tree 410. The exampleembodiments can therefore implement the smart contract method forstoring anonymous data via Merkle trees based on zero-knowledge proofsfor privacy preserving anomalous behavior detection on the blockchain,and the enhancement incorporating BufferKeys to the API and Blockchainledger system for efficiently implementing the Merkletree/zero-knowledge proof method to minimize conflicts. Note that theabove issue of conflicts arises in blockchain networks where thetransactions are executed, ordered and then committed—such asHyperledger Fabric v1, and the enhancements described above areapplicable to such blockchain networks.

FIG. 5A illustrates a method 510 of updating anonymous behavior on ablockchain structure, according to example embodiments. Referring toFIG. 5A, in 511, the method may include storing a tree structure via ablockchain storage. For example, the tree structure may include a Merkletree, a binary tree, a non-binary tree, and the like. The anonymousbehavior data may include anonymous behavior of a plurality ofblockchain participants stored in a plurality of nodes in a hierarchicalstructure. In some embodiments, the tree structure may include aplurality of active leaf nodes storing anonymous behavior data for aplurality of blockchain participants, respectively, which do not revealidentities of the plurality of blockchain participants. The anonymousbehavior may like an identity of the provider of the content. Forexample, the anonymous behavior may not identify a public key, a networkaddress, a name, a device ID, an email address, a username, or the like,associated with the behavior.

In 512, the method may include receiving a request to add new anonymousbehavior data to the tree structure. For example, the request mayinclude a zero-knowledge proof generated by a blockchain participant, anullifier of a previous active leaf of the blockchain participant, a newactive leaf (anonymous data), and the like. For example, thezero-knowledge proof may include a random string that is known only tothe blockchain participant which can be used to verify variousattributes of the new active leaf node and its contents withoutrevealing an identity of the blockchain participant. In someembodiments, the method may further include verifying a validity of thenew anonymous behavior based on a root value of the tree structure, thezero-knowledge proof, and anonymous attributes of the new anonymousbehavior.

In 513, the method may include identifying an active leaf on the treestructure which stores previously recorded anonymous behavior data ofthe blockchain participant associated with the request based on thezero-knowledge proof. In 514, the method may include generating a newactive leaf for the blockchain participant based on the new anonymousbehavior data and the previously recorded anonymous behavior. Here, thenew active leaf may be used to replace the current active leaf. In someembodiments, the method may further include further include nullifyingthe identified active leaf on the tree structure with the new activeleaf in response to receipt of the new anonymous behavior data. In 515,the method may include storing the new active leaf as a leaf node on thetree structure in the blockchain storage.

In some embodiments, the tree structure may include a Merkle tree whichis stored via a key-value store of the blockchain storage, and theMerkle tree may include a respective active leaf node for eachparticipant of the blockchain. In some embodiments, the anonymousbehavior data may include anonymous reviews submitted by the blockchainparticipant. In some embodiments, the method may further includeendorsing the new active leaf based on the zero-knowledge proof, priorto storing the new active leaf on the tree structure.

FIG. 5B illustrates a method 520 of managing a queue via a blockchainledger, according to example embodiments. Here, the queue may be used toprevent conflicts from occurring when multiple participants attempt toadd content to a blockchain storage structure at the same time.Referring to FIG. 5B, in 521, the method may include receiving a contentrequest to add a content to a blockchain storage structure implementedon a blockchain database. For example, the content request may include arequest to store a new node (e.g., an active leaf node, etc.) on ashared blockchain storage structure such as a binary tree, Merkle tree,etc. In some embodiments, the content request may include anonymouscontent that does not reveal an identity of a content creator. Here, theblockchain storage structure may store anonymous content of a pluralityof content creators.

In 522, the method may include temporarily storing the content of thecontent request in a queue implemented via the blockchain database basedon when the request is received. The queue may be implemented via adistributed ledger and controlled by a smart contract executing on peernodes with the blockchain. In some embodiments, the queue may include afirst-in first-out (FIFO) queue which is implemented via execute of thesmart contract (chaincode) of the blockchain database. In 523, themethod may include receiving a request to flush the queue which isinvoked by chaincode. In response to the flush request, in 524, themethod may include removing the content from the queue and adding thecontent to the blockchain storage structure. For example, the removingmay include pushing the content from an end of the FIFO queue to a newnode on a tree structure stored on the blockchain database.

In some embodiments, the receiving may include receiving a plurality ofcontent requests to add a plurality of pieces of content to theblockchain storage structure, and the temporarily storing may includetemporarily storing each piece of content as a respective entry in thequeue. Here, the content may include new leaf nodes to be added asactive leaf nodes to a Merkle tree. The nodes in the queue may beordered based on when they are received so as to ensure correctchronological order. In some embodiments, the removing may includeadding the content to an active leaf node on a Merkle tree storagestructure implemented via the blockchain database. In some embodiments,the Merkle tree storage structure may be maintained within a key-valuestore (KVS) of the blockchain database.

FIG. 6A illustrates an example system 600 that includes a physicalinfrastructure 610 configured to perform various operations according toexample embodiments. Referring to FIG. 6A, the physical infrastructure610 includes a module 612 and a module 614. The module 614 includes ablockchain 620 and a smart contract 630 (which may reside on theblockchain 620), that may execute any of the operational steps 608 (inmodule 612) included in any of the example embodiments. Thesteps/operations 608 may include one or more of the embodimentsdescribed or depicted and may represent output or written informationthat is written or read from one or more smart contracts 630 and/orblockchains 620. The physical infrastructure 610, the module 612, andthe module 614 may include one or more computers, servers, processors,memories, and/or wireless communication devices. Further, the module 612and the module 614 may be a same module.

FIG. 6B illustrates another example system 640 configured to performvarious operations according to example embodiments. Referring to FIG.6B, the system 640 includes a module 612 and a module 614. The module614 includes a blockchain 620 and a smart contract 630 (which may resideon the blockchain 620), that may execute any of the operational steps608 (in module 612) included in any of the example embodiments. Thesteps/operations 608 may include one or more of the embodimentsdescribed or depicted and may represent output or written informationthat is written or read from one or more smart contracts 630 and/orblockchains 620. The physical infrastructure 610, the module 612, andthe module 614 may include one or more computers, servers, processors,memories, and/or wireless communication devices. Further, the module 612and the module 614 may be a same module.

FIG. 6C illustrates an example system configured to utilize a smartcontract configuration among contracting parties and a mediating serverconfigured to enforce the smart contract terms on the blockchainaccording to example embodiments. Referring to FIG. 6C, theconfiguration 650 may represent a communication session, an assettransfer session or a process or procedure that is driven by a smartcontract 630 which explicitly identifies one or more user devices 652and/or 656. The execution, operations and results of the smart contractexecution may be managed by a server 654. Content of the smart contract630 may require digital signatures by one or more of the entities 652and 656 which are parties to the smart contract transaction. The resultsof the smart contract execution may be written to a blockchain 620 as ablockchain transaction. The smart contract 630 resides on the blockchain620 which may reside on one or more computers, servers, processors,memories, and/or wireless communication devices.

FIG. 6D illustrates a system 660 including a blockchain, according toexample embodiments. Referring to the example of FIG. 6D, an applicationprogramming interface (API) gateway 662 provides a common interface foraccessing blockchain logic (e.g., smart contract 630 or other chaincode)and data (e.g., distributed ledger, etc.). In this example, the APIgateway 662 is a common interface for performing transactions (invoke,queries, etc.) on the blockchain by connecting one or more entities 652and 656 to a blockchain peer (i.e., server 654). Here, the server 654 isa blockchain network peer component that holds a copy of the world stateand a distributed ledger allowing clients 652 and 656 to query data onthe world state as well as submit transactions into the blockchainnetwork where, depending on the smart contract 630 and endorsementpolicy, endorsing peers will run the smart contracts 630.

The above embodiments may be implemented in hardware, in a computerprogram executed by a processor, in firmware, or in a combination of theabove. A computer program may be embodied on a computer readable medium,such as a storage medium. For example, a computer program may reside inrandom access memory (“RAM”), flash memory, read-only memory (“ROM”),erasable programmable read-only memory (“EPROM”), electrically erasableprogrammable read-only memory (“EEPROM”), registers, hard disk, aremovable disk, a compact disk read-only memory (“CD-ROM”), or any otherform of storage medium known in the art.

An exemplary storage medium may be coupled to the processor such thatthe processor may read information from, and write information to, thestorage medium. In the alternative, the storage medium may be integralto the processor. The processor and the storage medium may reside in anapplication specific integrated circuit (“ASIC”). In the alternative,the processor and the storage medium may reside as discrete components.

FIG. 7A illustrates a process 700 of a new block being added to adistributed ledger 720, according to example embodiments, and FIG. 7Billustrates contents of a new data block structure 730 for blockchain,according to example embodiments. Referring to FIG. 7A, clients (notshown) may submit transactions to blockchain nodes 711, 712, and/or 713.Clients may be instructions received from any source to enact activityon the blockchain 720. As an example, clients may be applications thatact on behalf of a requester, such as a device, person or entity topropose transactions for the blockchain. The plurality of blockchainpeers (e.g., blockchain nodes 711, 712, and 713) may maintain a state ofthe blockchain network and a copy of the distributed ledger 720.Different types of blockchain nodes/peers may be present in theblockchain network including endorsing peers which simulate and endorsetransactions proposed by clients and committing peers which verifyendorsements, validate transactions, and commit transactions to thedistributed ledger 720. In this example, the blockchain nodes 711, 712,and 713 may perform the role of endorser node, committer node, or both.

The distributed ledger 720 includes a blockchain which stores immutable,sequenced records in blocks, and a state database 724 (current worldstate) maintaining a current state of the blockchain 722. Onedistributed ledger 720 may exist per channel and each peer maintains itsown copy of the distributed ledger 720 for each channel of which theyare a member. The blockchain 722 is a transaction log, structured ashash-linked blocks where each block contains a sequence of Ntransactions. Blocks may include various components such as shown inFIG. 7B. The linking of the blocks (shown by arrows in FIG. 7A) may begenerated by adding a hash of a prior block's header within a blockheader of a current block. In this way, all transactions on theblockchain 722 are sequenced and cryptographically linked togetherpreventing tampering with blockchain data without breaking the hashlinks. Furthermore, because of the links, the latest block in theblockchain 722 represents every transaction that has come before it. Theblockchain 722 may be stored on a peer file system (local or attachedstorage), which supports an append-only blockchain workload.

The current state of the blockchain 722 and the distributed ledger 722may be stored in the state database 724. Here, the current state datarepresents the latest values for all keys ever included in the chaintransaction log of the blockchain 722. Chaincode invocations executetransactions against the current state in the state database 724. Tomake these chaincode interactions extremely efficient, the latest valuesof all keys are stored in the state database 724. The state database 724may include an indexed view into the transaction log of the blockchain722, it can therefore be regenerated from the chain at any time. Thestate database 724 may automatically get recovered (or generated ifneeded) upon peer startup, before transactions are accepted.

Endorsing nodes receive transactions from clients and endorse thetransaction based on simulated results. Endorsing nodes hold smartcontracts which simulate the transaction proposals. When an endorsingnode endorses a transaction, the endorsing nodes creates a transactionendorsement which is a signed response from the endorsing node to theclient application indicating the endorsement of the simulatedtransaction. The method of endorsing a transaction depends on anendorsement policy which may be specified within chaincode. An exampleof an endorsement policy is “the majority of endorsing peers mustendorse the transaction”. Different channels may have differentendorsement policies. Endorsed transactions are forward by the clientapplication to ordering service 710.

The ordering service 710 accepts endorsed transactions, orders them intoa block, and delivers the blocks to the committing peers. For example,the ordering service 710 may initiate a new block when a threshold oftransactions has been reached, a timer times out, or another condition.In the example of FIG. 7A, blockchain node 712 is a committing peer thathas received a new data new data block 730 for storage on blockchain720. The first block in the blockchain may be referred to as a genesisblock which includes information about the blockchain, its members, thedata stored therein, etc.

The ordering service 710 may be made up of a cluster of orderers. Theordering service 710 does not process transactions, smart contracts, ormaintain the shared ledger. Rather, the ordering service 710 may acceptthe endorsed transactions and specifies the order in which thosetransactions are committed to the distributed ledger 720. Thearchitecture of the blockchain network may be designed such that thespecific implementation of ‘ordering’ (e.g., Solo, Kafka, BFT, etc.)becomes a pluggable component.

Transactions are written to the distributed ledger 720 in a consistentorder. The order of transactions is established to ensure that theupdates to the state database 724 are valid when they are committed tothe network. Unlike a cryptocurrency blockchain system (e.g., Bitcoin,etc.) where ordering occurs through the solving of a cryptographicpuzzle, or mining, in this example the parties of the distributed ledger720 may choose the ordering mechanism that best suits that network.

When the ordering service 710 initializes a new data block 730, the newdata block 730 may be broadcast to committing peers (e.g., blockchainnodes 711, 712, and 713). In response, each committing peer validatesthe transaction within the new data block 730 by checking to make surethat the read set and the write set still match the current world statein the state database 724. Specifically, the committing peer candetermine whether the read data that existed when the endorserssimulated the transaction is identical to the current world state in thestate database 724. When the committing peer validates the transaction,the transaction is written to the blockchain 722 on the distributedledger 720, and the state database 724 is updated with the write datafrom the read-write set. If a transaction fails, that is, if thecommitting peer finds that the read-write set does not match the currentworld state in the state database 724, the transaction ordered into ablock will still be included in that block, but it will be marked asinvalid, and the state database 724 will not be updated.

Referring to FIG. 7B, a new data block 730 (also referred to as a datablock) that is stored on the blockchain 722 of the distributed ledger720 may include multiple data segments such as a block header 740, blockdata 750, and block metadata 760. It should be appreciated that thevarious depicted blocks and their contents, such as new data block 730and its contents. shown in FIG. 7B are merely examples and are not meantto limit the scope of the example embodiments. The new data block 730may store transactional information of N transaction(s) (e.g., 1, 10,100, 500, 1000, 2000, 3000, etc.) within the block data 750. The newdata block 730 may also include a link to a previous block (e.g., on theblockchain 722 in FIG. 7A) within the block header 740. In particular,the block header 740 may include a hash of a previous block's header.The block header 740 may also include a unique block number, a hash ofthe block data 750 of the new data block 730, and the like. The blocknumber of the new data block 730 may be unique and assigned in variousorders, such as an incremental/sequential order starting from zero.

The block data 750 may store transactional information of eachtransaction that is recorded within the new data block 730. For example,the transaction data may include one or more of a type of thetransaction, a version, a timestamp, a channel ID of the distributedledger 720, a transaction ID, an epoch, a payload visibility, achaincode path (deploy tx), a chaincode name, a chaincode version, input(chaincode and functions), a client (creator) identify such as a publickey and certificate, a signature of the client, identities of endorsers,endorser signatures, a proposal hash, chaincode events, response status,namespace, a read set (list of key and version read by the transaction,etc.), a write set (list of key and value, etc.), a start key, an endkey, a list of keys, a Merkel tree query summary, and the like. Thetransaction data may be stored for each of the N transactions.

In some embodiments, the block data 750 may also store anonymous data752 such as anonymous activity, behavior, participation, etc. of a userwithin a larger group of users. In doing so, the block data 750 includesadditional information which is added to the hash-linked chain of blocksin the blockchain 722. For example, the additional information mayinclude a Merkle tree (or other structure) including anonymous data 752of various sources. The anonymous data 752 may include a secret knownonly by the submitted of the data, an accumulation of behavior, a numberof entries on the Merkle tree, and the like. Accordingly, the anonymousdata 752 can be stored in an immutable ledger via a key-value storewhich is included in the distributed ledger 720. Some of the benefits ofstoring such anonymous data 752 are reflected in the various embodimentsdisclosed and depicted herein. Although in FIG. 7B the anonymous data752 is depicted in the block data 750, it could also be located in theblock header 740 or the block metadata 760, or other areas of thedistributed ledger besides the blockchain such as a key-value store, aworld-state database, and the like.

The block metadata 760 may store multiple fields of metadata (e.g., as abyte array, etc.). Metadata fields may include signature on blockcreation, a reference to a last configuration block, a transactionfilter identifying valid and invalid transactions within the block, lastoffset persisted of an ordering service that ordered the block, and thelike. The signature, the last configuration block, and the orderermetadata may be added by the ordering service 710. Meanwhile, acommitter of the block (such as blockchain node 712) may addvalidity/invalidity information based on an endorsement policy,verification of read/write sets, and the like. The transaction filtermay include a byte array of a size equal to the number of transactionsin the block data 750 and a validation code identifying whether atransaction was valid/invalid.

FIG. 7C illustrates an embodiment of a blockchain 770 for digitalcontent in accordance with the embodiments described herein. The digitalcontent may include one or more files and associated information. Thefiles may include media, images, video, audio, text, links, graphics,animations, web pages, documents, or other forms of digital content. Theimmutable, append-only aspects of the blockchain serve as a safeguard toprotect the integrity, validity, and authenticity of the digitalcontent, making it suitable use in legal proceedings where admissibilityrules apply or other settings where evidence is taken in toconsideration or where the presentation and use of digital informationis otherwise of interest. In this case, the digital content may bereferred to as digital evidence.

The blockchain may be formed in various ways. In one embodiment, thedigital content may be included in and accessed from the blockchainitself. For example, each block of the blockchain may store a hash valueof reference information (e.g., header, value, etc.) along theassociated digital content. The hash value and associated digitalcontent may then be encrypted together. Thus, the digital content ofeach block may be accessed by decrypting each block in the blockchain,and the hash value of each block may be used as a basis to reference aprevious block. This may be illustrated as follows:

Block 1 Block 2 Block N Hash Value 1 Hash Value 2 Hash Value N DigitalContent 1 Digital Content 2 Digital Content N

In one embodiment, the digital content may be not included in theblockchain. For example, the blockchain may store the encrypted hashesof the content of each block without any of the digital content. Thedigital content may be stored in another storage area or memory addressin association with the hash value of the original file. The otherstorage area may be the same storage device used to store the blockchainor may be a different storage area or even a separate relationaldatabase. The digital content of each block may be referenced oraccessed by obtaining or querying the hash value of a block of interestand then looking up that has value in the storage area, which is storedin correspondence with the actual digital content. This operation may beperformed, for example, a database gatekeeper. This may be illustratedas follows:

Blockchain Storage Area Block 1 Hash Value Block 1 Hash Value . . .Content . . . . . . Block N Hash Value Block N Hash Value . . . Content

In the example embodiment of FIG. 7C, the blockchain 770 includes anumber of blocks 778 ₁, 778 ₂, . . . 778 _(N) cryptographically linkedin an ordered sequence, where N≥1. The encryption used to link theblocks 778 ₁, 778 ₂, . . . 778 _(N) may be any of a number of keyed orun-keyed Hash functions. In one embodiment, the blocks 778 ₁, 778 ₂, . .. 778 _(N) are subject to a hash function which produces n-bitalphanumeric outputs (where n is 256 or another number) from inputs thatare based on information in the blocks. Examples of such a hash functioninclude, but are not limited to, a SHA-type (SHA stands for Secured HashAlgorithm) algorithm, Merkle-Damgard algorithm, HAIFA algorithm,Merkle-tree algorithm, nonce-based algorithm, and anon-collision-resistant PRF algorithm. In another embodiment, the blocks778 ₁, 778 ₂, . . . , 778 _(N) may be cryptographically linked by afunction that is different from a hash function. For purposes ofillustration, the following description is made with reference to a hashfunction, e.g., SHA-2.

Each of the blocks 778 ₁, 778 ₂, . . . , 778 _(N) in the blockchainincludes a header, a version of the file, and a value. The header andthe value are different for each block as a result of hashing in theblockchain. In one embodiment, the value may be included in the header.As described in greater detail below, the version of the file may be theoriginal file or a different version of the original file.

The first block 778 ₁ in the blockchain is referred to as the genesisblock and includes the header 772 ₁, original file 774 ₁, and an initialvalue 776 ₁. The hashing scheme used for the genesis block, and indeedin all subsequent blocks, may vary. For example, all the information inthe first block 778 ₁ may be hashed together and at one time, or each ora portion of the information in the first block 778 ₁ may be separatelyhashed and then a hash of the separately hashed portions may beperformed.

The header 772 ₁ may include one or more initial parameters, which, forexample, may include a version number, timestamp, nonce, rootinformation, difficulty level, consensus protocol, duration, mediaformat, source, descriptive keywords, and/or other informationassociated with original file 774 ₁ and/or the blockchain. The header772 ₁ may be generated automatically (e.g., by blockchain networkmanaging software) or manually by a blockchain participant. Unlike theheader in other blocks 778 ₂ to 778 _(N) in the blockchain, the header772 ₁ in the genesis block does not reference a previous block, simplybecause there is no previous block.

The original file 774 ₁ in the genesis block may be, for example, dataas captured by a device with or without processing prior to itsinclusion in the blockchain. The original file 774 ₁ is received throughthe interface of the system from the device, media source, or node. Theoriginal file 774 ₁ is associated with metadata, which, for example, maybe generated by a user, the device, and/or the system processor, eithermanually or automatically. The metadata may be included in the firstblock 778 ₁ in association with the original file 774 ₁.

The value 776 ₁ in the genesis block is an initial value generated basedon one or more unique attributes of the original file 774 ₁. In oneembodiment, the one or more unique attributes may include the hash valuefor the original file 774 ₁, metadata for the original file 774 ₁, andother information associated with the file. In one implementation, theinitial value 776 ₁ may be based on the following unique attributes:

-   -   1) SHA-2 computed hash value for the original file    -   2) originating device ID    -   3) starting timestamp for the original file    -   4) initial storage location of the original file    -   5) blockchain network member ID for software to currently        control the original file and associated metadata

The other blocks 778 ₂ to 778 _(N) in the blockchain also have headers,files, and values. However, unlike the first block 772 ₁, each of theheaders 772 ₂ to 772 _(N) in the other blocks includes the hash value ofan immediately preceding block. The hash value of the immediatelypreceding block may be just the hash of the header of the previous blockor may be the hash value of the entire previous block. By including thehash value of a preceding block in each of the remaining blocks, a tracecan be performed from the Nth block back to the genesis block (and theassociated original file) on a block-by-block basis, as indicated byarrows 780, to establish an auditable and immutable chain-of-custody.

Each of the header 772 ₂ to 772 _(N) in the other blocks may alsoinclude other information, e.g., version number, timestamp, nonce, rootinformation, difficulty level, consensus protocol, and/or otherparameters or information associated with the corresponding files and/orthe blockchain in general.

The files 774 ₂ to 774 _(N) in the other blocks may be equal to theoriginal file or may be a modified version of the original file in thegenesis block depending, for example, on the type of processingperformed. The type of processing performed may vary from block toblock. The processing may involve, for example, any modification of afile in a preceding block, such as redacting information or otherwisechanging the content of, taking information away from, or adding orappending information to the files.

Additionally, or alternatively, the processing may involve merelycopying the file from a preceding block, changing a storage location ofthe file, analyzing the file from one or more preceding blocks, movingthe file from one storage or memory location to another, or performingaction relative to the file of the blockchain and/or its associatedmetadata. Processing which involves analyzing a file may include, forexample, appending, including, or otherwise associating variousanalytics, statistics, or other information associated with the file.

The values in each of the other blocks 776 ₂ to 776 _(N) in the otherblocks are unique values and are all different as a result of theprocessing performed. For example, the value in any one blockcorresponds to an updated version of the value in the previous block.The update is reflected in the hash of the block to which the value isassigned. The values of the blocks therefore provide an indication ofwhat processing was performed in the blocks and also permit a tracingthrough the blockchain back to the original file. This tracking confirmsthe chain-of-custody of the file throughout the entire blockchain.

For example, consider the case where portions of the file in a previousblock are redacted, blocked out, or pixelated in order to protect theidentity of a person shown in the file. In this case, the blockincluding the redacted file will include metadata associated with theredacted file, e.g., how the redaction was performed, who performed theredaction, timestamps where the redaction(s) occurred, etc. The metadatamay be hashed to form the value. Because the metadata for the block isdifferent from the information that was hashed to form the value in theprevious block, the values are different from one another and may berecovered when decrypted.

In one embodiment, the value of a previous block may be updated (e.g., anew hash value computed) to form the value of a current block when anyone or more of the following occurs. The new hash value may be computedby hashing all or a portion of the information noted below, in thisexample embodiment.

-   -   a) new SHA-2 computed hash value if the file has been processed        in any way (e.g., if the file was redacted, copied, altered,        accessed, or some other action was taken)    -   b) new storage location for the file    -   c) new metadata identified associated with the file    -   d) transfer of access or control of the file from one blockchain        participant to another blockchain participant

FIG. 7D illustrates an embodiment of a block which may represent thestructure of the blocks in the blockchain 790 in accordance with oneembodiment. The block, Block_(i), includes a header 772 _(i), a file 774_(i), and a value 776 _(i).

The header 772 _(i) includes a hash value of a previous blockBlock_(i-1) and additional reference information, which, for example,may be any of the types of information (e.g., header informationincluding references, characteristics, parameters, etc.) discussedherein. All blocks reference the hash of a previous block except, ofcourse, the genesis block. The hash value of the previous block may bejust a hash of the header in the previous block or a hash of all or aportion of the information in the previous block, including the file andmetadata.

The file 774 _(i) includes a plurality of data, such as Data 1, Data 2,. . . , Data N in sequence. The data are tagged with metadata Metadata1, Metadata 2, . . . , Metadata N which describe the content and/orcharacteristics associated with the data. For example, the metadata foreach data may include information to indicate a timestamp for the data,process the data, keywords indicating the persons or other contentdepicted in the data, and/or other features that may be helpful toestablish the validity and content of the file as a whole, andparticularly its use a digital evidence, for example, as described inconnection with an embodiment discussed below. In addition to themetadata, each data may be tagged with reference REF₁, REF₂, . . . ,REF_(N) to a previous data to prevent tampering, gaps in the file, andsequential reference through the file.

Once the metadata is assigned to the data (e.g., through a smartcontract), the metadata cannot be altered without the hash changing,which can easily be identified for invalidation. The metadata, thus,creates a data log of information that may be accessed for use byparticipants in the blockchain.

The value 776 _(i) is a hash value or other value computed based on anyof the types of information previously discussed. For example, for anygiven block Block_(i), the value for that block may be updated toreflect the processing that was performed for that block, e.g., new hashvalue, new storage location, new metadata for the associated file,transfer of control or access, identifier, or other action orinformation to be added. Although the value in each block is shown to beseparate from the metadata for the data of the file and header, thevalue may be based, in part or whole, on this metadata in anotherembodiment.

Once the blockchain 770 is formed, at any point in time, the immutablechain-of-custody for the file may be obtained by querying the blockchainfor the transaction history of the values across the blocks. This query,or tracking procedure, may begin with decrypting the value of the blockthat is most currently included (e.g., the last (N^(th)) block), andthen continuing to decrypt the value of the other blocks until thegenesis block is reached and the original file is recovered. Thedecryption may involve decrypting the headers and files and associatedmetadata at each block, as well.

Decryption is performed based on the type of encryption that took placein each block. This may involve the use of private keys, public keys, ora public key-private key pair. For example, when asymmetric encryptionis used, blockchain participants or a processor in the network maygenerate a public key and private key pair using a predeterminedalgorithm. The public key and private key are associated with each otherthrough some mathematical relationship. The public key may bedistributed publicly to serve as an address to receive messages fromother users, e.g., an IP address or home address. The private key iskept secret and used to digitally sign messages sent to other blockchainparticipants. The signature is included in the message so that therecipient can verify using the public key of the sender. This way, therecipient can be sure that only the sender could have sent this message.

Generating a key pair may be analogous to creating an account on theblockchain, but without having to actually register anywhere. Also,every transaction that is executed on the blockchain is digitally signedby the sender using their private key. This signature ensures that onlythe owner of the account can track and process (if within the scope ofpermission determined by a smart contract) the file of the blockchain.

FIG. 8 illustrates an example system 800 that supports one or more ofthe example embodiments described and/or depicted herein. The system 800comprises a computer system/server 802, which is operational withnumerous other general purpose or special purpose computing systemenvironments or configurations. Examples of well-known computingsystems, environments, and/or configurations that may be suitable foruse with computer system/server 802 include, but are not limited to,personal computer systems, server computer systems, thin clients, thickclients, hand-held or laptop devices, multiprocessor systems,microprocessor-based systems, set top boxes, programmable consumerelectronics, network PCs, minicomputer systems, mainframe computersystems, and distributed cloud computing environments that include anyof the above systems or devices, and the like.

Computer system/server 802 may be described in the general context ofcomputer system-executable instructions, such as program modules, beingexecuted by a computer system. Generally, program modules may includeroutines, programs, objects, components, logic, data structures, and soon that perform particular tasks or implement particular abstract datatypes. Computer system/server 802 may be practiced in distributed cloudcomputing environments where tasks are performed by remote processingdevices that are linked through a communications network. In adistributed cloud computing environment, program modules may be locatedin both local and remote computer system storage media including memorystorage devices.

As shown in FIG. 8, computer system/server 802 in cloud computing node800 is shown in the form of a general-purpose computing device. Thecomponents of computer system/server 802 may include, but are notlimited to, one or more processors or processing units 804, a systemmemory 806, and a bus that couples various system components includingsystem memory 806 to processor 804.

The bus represents one or more of any of several types of busstructures, including a memory bus or memory controller, a peripheralbus, an accelerated graphics port, and a processor or local bus usingany of a variety of bus architectures. By way of example, and notlimitation, such architectures include Industry Standard Architecture(ISA) bus, Micro Channel Architecture (MCA) bus, Enhanced ISA (EISA)bus, Video Electronics Standards Association (VESA) local bus, andPeripheral Component Interconnects (PCI) bus.

Computer system/server 802 typically includes a variety of computersystem readable media. Such media may be any available media that isaccessible by computer system/server 802, and it includes both volatileand non-volatile media, removable and non-removable media. System memory806, in one embodiment, implements the flow diagrams of the otherfigures. The system memory 806 can include computer system readablemedia in the form of volatile memory, such as random-access memory (RAM)810 and/or cache memory 812. Computer system/server 802 may furtherinclude other removable/non-removable, volatile/non-volatile computersystem storage media. By way of example only, storage system 814 can beprovided for reading from and writing to a non-removable, non-volatilemagnetic media (not shown and typically called a “hard drive”). Althoughnot shown, a magnetic disk drive for reading from and writing to aremovable, non-volatile magnetic disk (e.g., a “floppy disk”), and anoptical disk drive for reading from or writing to a removable,non-volatile optical disk such as a CD-ROM, DVD-ROM or other opticalmedia can be provided. In such instances, each can be connected to thebus by one or more data media interfaces. As will be further depictedand described below, memory 806 may include at least one program producthaving a set (e.g., at least one) of program modules that are configuredto carry out the functions of various embodiments of the application.

Program/utility 816, having a set (at least one) of program modules 818,may be stored in memory 806 by way of example, and not limitation, aswell as an operating system, one or more application programs, otherprogram modules, and program data. Each of the operating system, one ormore application programs, other program modules, and program data orsome combination thereof, may include an implementation of a networkingenvironment. Program modules 818 generally carry out the functionsand/or methodologies of various embodiments of the application asdescribed herein.

As will be appreciated by one skilled in the art, aspects of the presentapplication may be embodied as a system, method, or computer programproduct. Accordingly, aspects of the present application may take theform of an entirely hardware embodiment, an entirely software embodiment(including firmware, resident software, micro-code, etc.) or anembodiment combining software and hardware aspects that may allgenerally be referred to herein as a “circuit,” “module” or “system.”Furthermore, aspects of the present application may take the form of acomputer program product embodied in one or more computer readablemedium(s) having computer readable program code embodied thereon.

Computer system/server 802 may also communicate with one or moreexternal devices 820 such as a keyboard, a pointing device, a display822, etc.; one or more devices that enable a user to interact withcomputer system/server 802; and/or any devices (e.g., network card,modem, etc.) that enable computer system/server 802 to communicate withone or more other computing devices. Such communication can occur viaI/O interfaces 824. Still yet, computer system/server 802 cancommunicate with one or more networks such as a local area network(LAN), a general wide area network (WAN), and/or a public network (e.g.,the Internet) via network adapter 826. As depicted, network adapter 826communicates with the other components of computer system/server 802 viaa bus. It should be understood that although not shown, other hardwareand/or software components could be used in conjunction with computersystem/server 802. Examples, include, but are not limited to: microcode,device drivers, redundant processing units, external disk drive arrays,RAID systems, tape drives, and data archival storage systems, etc.

Although an exemplary embodiment of at least one of a system, method,and non-transitory computer readable medium has been illustrated in theaccompanied drawings and described in the foregoing detaileddescription, it will be understood that the application is not limitedto the embodiments disclosed, but is capable of numerous rearrangements,modifications, and substitutions as set forth and defined by thefollowing claims. For example, the capabilities of the system of thevarious figures can be performed by one or more of the modules orcomponents described herein or in a distributed architecture and mayinclude a transmitter, receiver or pair of both. For example, all orpart of the functionality performed by the individual modules, may beperformed by one or more of these modules. Further, the functionalitydescribed herein may be performed at various times and in relation tovarious events, internal or external to the modules or components. Also,the information sent between various modules can be sent between themodules via at least one of: a data network, the Internet, a voicenetwork, an Internet Protocol network, a wireless device, a wired deviceand/or via plurality of protocols. Also, the messages sent or receivedby any of the modules may be sent or received directly and/or via one ormore of the other modules.

One skilled in the art will appreciate that a “system” could be embodiedas a personal computer, a server, a console, a personal digitalassistant (PDA), a cell phone, a tablet computing device, a smartphoneor any other suitable computing device, or combination of devices.Presenting the above-described functions as being performed by a“system” is not intended to limit the scope of the present applicationin any way but is intended to provide one example of many embodiments.Indeed, methods, systems and apparatuses disclosed herein may beimplemented in localized and distributed forms consistent with computingtechnology.

It should be noted that some of the system features described in thisspecification have been presented as modules, in order to moreparticularly emphasize their implementation independence. For example, amodule may be implemented as a hardware circuit comprising custom verylarge-scale integration (VLSI) circuits or gate arrays, off-the-shelfsemiconductors such as logic chips, transistors, or other discretecomponents. A module may also be implemented in programmable hardwaredevices such as field programmable gate arrays, programmable arraylogic, programmable logic devices, graphics processing units, or thelike.

A module may also be at least partially implemented in software forexecution by various types of processors. An identified unit ofexecutable code may, for instance, comprise one or more physical orlogical blocks of computer instructions that may, for instance, beorganized as an object, procedure, or function. Nevertheless, theexecutables of an identified module need not be physically locatedtogether but may comprise disparate instructions stored in differentlocations which, when joined logically together, comprise the module andachieve the stated purpose for the module. Further, modules may bestored on a computer-readable medium, which may be, for instance, a harddisk drive, flash device, random access memory (RAM), tape, or any othersuch medium used to store data.

Indeed, a module of executable code could be a single instruction, ormany instructions, and may even be distributed over several differentcode segments, among different programs, and across several memorydevices. Similarly, operational data may be identified and illustratedherein within modules and may be embodied in any suitable form andorganized within any suitable type of data structure. The operationaldata may be collected as a single data set or may be distributed overdifferent locations including over different storage devices, and mayexist, at least partially, merely as electronic signals on a system ornetwork.

It will be readily understood that the components of the application, asgenerally described and illustrated in the figures herein, may bearranged and designed in a wide variety of different configurations.Thus, the detailed description of the embodiments is not intended tolimit the scope of the application as claimed but is merelyrepresentative of selected embodiments of the application.

One having ordinary skill in the art will readily understand that theabove may be practiced with steps in a different order, and/or withhardware elements in configurations that are different than those whichare disclosed. Therefore, although the application has been describedbased upon these preferred embodiments, it would be apparent to those ofskill in the art that certain modifications, variations, and alternativeconstructions would be apparent.

While preferred embodiments of the present application have beendescribed, it is to be understood that the embodiments described areillustrative only and the scope of the application is to be definedsolely by the appended claims when considered with a full range ofequivalents and modifications (e.g., protocols, hardware devices,software platforms etc.) thereto.

What is claimed is:
 1. A computing system comprising: a storageconfigured to store a tree structure, the tree structure comprisinganonymous behavior data of a plurality of blockchain participants storedin a plurality of nodes in a hierarchical structure; and a processor,implemented in hardware, configured to receive a request to add newanonymous behavior data to the tree structure which comprises azero-knowledge proof generated by a blockchain participant, identify anactive leaf on the tree structure which stores previously recordedanonymous behavior data of the blockchain participant associated withthe request based on the zero-knowledge proof, and generate a new activeleaf for the blockchain participant based on the new anonymous behaviordata and the previously recorded anonymous behavior data, wherein thestorage is further configured to store the new active leaf as a leafnode on the tree structure.
 2. The computing system of claim 1, whereinthe tree structure of the storage comprises a plurality of active leafnodes which store anonymous behavior data for the plurality ofblockchain participants, respectively, which do not reveal identities ofthe plurality of blockchain participants.
 3. The computing system ofclaim 1, wherein the processor is further configured to nullify theidentified active leaf on the tree structure with the new active leaf inresponse to receipt of the new anonymous behavior data.
 4. The computingsystem of claim 1, wherein the zero-knowledge proof comprises a randomstring that is known only to the blockchain participant.
 5. Thecomputing system of claim 1, wherein the processor is further configuredto verify a validity of the new anonymous behavior based on a root valueof the tree structure, the zero-knowledge proof, and anonymousattributes of the new anonymous behavior.
 6. The computing system ofclaim 1, wherein the tree structure comprises a Merkle tree which isstored via a key-value store of the storage, and the Merkle treecomprises a respective active leaf node for each of the plurality ofblockchain participants.
 7. The computing system of claim 1, wherein thenew anonymous behavior data comprises anonymous reviews submitted by theblockchain participant.
 8. The computing system of claim 1, wherein theprocessor is further configured to endorse the new active leaf based onthe zero-knowledge proof, prior to storage of the new active leaf on thetree structure.
 9. A method comprising: storing a tree structure via ablockchain storage, the tree structure comprising anonymous behaviordata of a plurality of blockchain participants stored in a plurality ofnodes in a hierarchical structure; receiving a request to add newanonymous behavior data to the tree structure, the request comprising azero-knowledge proof generated by a blockchain participant; identifyingan active leaf on the tree structure which stores previously recordedanonymous behavior data of the blockchain participant associated withthe request based on the zero-knowledge proof, generating a new activeleaf for the blockchain participant based on the new anonymous behaviordata and the previously recorded anonymous behavior data; and storingthe new active leaf as a leaf node on the tree structure in theblockchain storage.
 10. The method of claim 9, wherein the treestructure in the blockchain storage comprises a plurality of active leafnodes storing anonymous behavior data for the plurality of blockchainparticipants, respectively, which do not reveal identities of theplurality of blockchain participants.
 11. The method of claim 9, furthercomprising nullifying the identified active leaf on the tree structurewith the new active leaf in response to receipt of the new anonymousbehavior data.
 12. The method of claim 9, wherein the zero-knowledgeproof comprises a random string that is known only to the blockchainparticipant.
 13. The method of claim 9, further comprising verifying avalidity of the new anonymous behavior based on a root value of the treestructure, the zero-knowledge proof, and anonymous attributes of the newanonymous behavior data.
 14. The method of claim 9, wherein the treestructure comprises a Merkle tree which is stored via a key-value storeof the blockchain storage, and the Merkle tree comprises a respectiveactive leaf node for each of the plurality of blockchain participants.15. The method of claim 9, wherein the new anonymous behavior datacomprises anonymous reviews submitted by the blockchain participant. 16.The method of claim 9, further comprising endorsing the new active leafbased on the zero-knowledge proof, prior to storing the new active leafon the tree structure.
 17. A non-transitory computer readable mediumcomprising instructions, that when executed by a processor, cause theprocessor to perform a method comprising: storing a tree structure via ablockchain storage, the tree structure comprising anonymous behaviordata of a plurality of blockchain participants stored in a plurality ofnodes in a hierarchical structure; receiving a request to add newanonymous behavior data to the tree structure, the request comprising azero-knowledge proof generated by a blockchain participant; identifyingan active leaf on the tree structure which stores previously recordedanonymous behavior data of the blockchain participant associated withthe request based on the zero-knowledge proof, generating a new activeleaf for the blockchain participant based on the new anonymous behaviordata and the previously recorded anonymous behavior data; and storingthe new active leaf as a leaf node on the tree structure in theblockchain storage.
 18. The non-transitory computer-readable medium ofclaim 17, wherein the tree structure in the blockchain storage comprisesa plurality of active leaf nodes storing anonymous behavior data for theplurality of blockchain participants, respectively, which do not revealidentities of the plurality of blockchain participants.
 19. Thenon-transitory computer-readable medium of claim 17, wherein the methodfurther comprises nullifying the identified active leaf on the treestructure with the new active leaf in response to receipt of the newanonymous behavior data.
 20. The non-transitory computer-readable mediumof claim 17, wherein the zero-knowledge proof comprises a random stringthat is known only to the blockchain participant.